In terms of R-factor, I'm not sure how much I can believe what each manufacturer claims. DRV appears to have a good R-factor, but Lifestyle's is even better, while Excel's is rather poor according to their data. Nuwa is pretty poor as well, and Redwood is almost DRV level, which is hard to believe.
Arctic fox with its 4-season claim has a really bad R-factor...
Despite this, I've seen Excel owners claiming they had no issues camping at below freezing temperatures without any issues while Montana owners did at the same site (Montana has a better R-factor value than Excel on paper).